clk: si570: Add a driver for SI570 oscillators

Add a driver for SILabs 570, 571, 598, 599 programmable oscillators.
The devices generate low-jitter clock signals and are reprogrammable via
an I2C interface.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

4 files changed, 581 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/clock/silabs,si570.txt b/Documentation/devicetree/bindings/clock/silabs,si570.txt
new file mode 100644
index 000000000000..c09f21e1d98f
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/silabs,si570.txt
@@ -0,0 +1,39 @@
+Binding for Silicon Labs 570, 571, 598 and 599 programmable
+I2C clock generators.
+
+Reference
+This binding uses the common clock binding[1]. Details about the devices can be
+found in the data sheets[2][3].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+[2] Si570/571 Data Sheet
+    http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf
+[3] Si598/599 Data Sheet
+    http://www.silabs.com/Support%20Documents/TechnicalDocs/si598-99.pdf
+
+Required properties:
+ - compatible: Shall be one of "silabs,si570", "silabs,si571",
+                               "silabs,si598", "silabs,si599"
+ - reg: I2C device address.
+ - #clock-cells: From common clock bindings: Shall be 0.
+ - factory-fout: Factory set default frequency. This frequency is part specific.
+                 The correct frequency for the part used has to be provided in
+                 order to generate the correct output frequencies. For more
+                 details, please refer to the data sheet.
+ - temperature-stability: Temperature stability of the device in PPM. Should be
+                          one of: 7, 20, 50 or 100.
+
+Optional properties:
+ - clock-output-names: From common clock bindings. Recommended to be "si570".
+ - clock-frequency: Output frequency to generate. This defines the output
+                    frequency set during boot. It can be reprogrammed during
+                    runtime through the common clock framework.
+
+Example:
+        si570: clock-generator@5d {
+                #clock-cells = <0>;
+                compatible = "silabs,si570";
+                temperature-stability = <50>;
+                reg = <0x5d>;
+                factory-fout = <156250000>;
+        };
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 5c51115081b3..3089f05ba661 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -64,6 +64,16 @@ config COMMON_CLK_SI5351
           This driver supports Silicon Labs 5351A/B/C programmable clock
           generators.
 
+config COMMON_CLK_SI570
+        tristate "Clock driver for SiLabs 570 and compatible devices"
+        depends on I2C
+        depends on OF
+        select REGMAP_I2C
+        help
+        ---help---
+          This driver supports Silicon Labs 570/571/598/599 programmable
+          clock generators.
+
 config COMMON_CLK_S2MPS11
         tristate "Clock driver for S2MPS11 MFD"
         depends on MFD_SEC_CORE
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 2460afd59405..6705d9a82cbc 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -45,6 +45,7 @@ obj-$(CONFIG_COMMON_CLK_AXI_CLKGEN) += clk-axi-clkgen.o
 obj-$(CONFIG_COMMON_CLK_WM831X) += clk-wm831x.o
 obj-$(CONFIG_COMMON_CLK_MAX77686) += clk-max77686.o
 obj-$(CONFIG_COMMON_CLK_SI5351) += clk-si5351.o
+obj-$(CONFIG_COMMON_CLK_SI570) += clk-si570.o
 obj-$(CONFIG_COMMON_CLK_S2MPS11) += clk-s2mps11.o
 obj-$(CONFIG_CLK_TWL6040)       += clk-twl6040.o
 obj-$(CONFIG_CLK_PPC_CORENET)   += clk-ppc-corenet.o
diff --git a/drivers/clk/clk-si570.c b/drivers/clk/clk-si570.c
new file mode 100644
index 000000000000..5d0ac9f8e1ee
--- /dev/null
+++ b/drivers/clk/clk-si570.c
@@ -0,0 +1,531 @@
+/*
+ * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
+ *
+ * Copyright (C) 2010, 2011 Ericsson AB.
+ * Copyright (C) 2011 Guenter Roeck.
+ * Copyright (C) 2011 - 2013 Xilinx Inc.
+ *
+ * Author: Guenter Roeck <guenter.roeck@ericsson.com>
+ *         Sören Brinkmann <soren.brinkmann@xilinx.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/* Si570 registers */
+#define SI570_REG_HS_N1         7
+#define SI570_REG_N1_RFREQ0     8
+#define SI570_REG_RFREQ1        9
+#define SI570_REG_RFREQ2        10
+#define SI570_REG_RFREQ3        11
+#define SI570_REG_RFREQ4        12
+#define SI570_REG_CONTROL       135
+#define SI570_REG_FREEZE_DCO    137
+#define SI570_DIV_OFFSET_7PPM   6
+
+#define HS_DIV_SHIFT            5
+#define HS_DIV_MASK             0xe0
+#define HS_DIV_OFFSET           4
+#define N1_6_2_MASK             0x1f
+#define N1_1_0_MASK             0xc0
+#define RFREQ_37_32_MASK        0x3f
+
+#define SI570_MIN_FREQ          10000000L
+#define SI570_MAX_FREQ          1417500000L
+#define SI598_MAX_FREQ          525000000L
+
+#define FDCO_MIN                4850000000LL
+#define FDCO_MAX                5670000000LL
+
+#define SI570_CNTRL_RECALL      (1 << 0)
+#define SI570_CNTRL_FREEZE_M    (1 << 5)
+#define SI570_CNTRL_NEWFREQ     (1 << 6)
+
+#define SI570_FREEZE_DCO        (1 << 4)
+
+/**
+ * struct clk_si570:
+ * @hw: Clock hw struct
+ * @regmap:     Device's regmap
+ * @div_offset: Rgister offset for dividers
+ * @max_freq:   Maximum frequency for this device
+ * @fxtal:      Factory xtal frequency
+ * @n1:         Clock divider N1
+ * @hs_div:     Clock divider HSDIV
+ * @rfreq:      Clock multiplier RFREQ
+ * @frequency:  Current output frequency
+ * @i2c_client: I2C client pointer
+ */
+struct clk_si570 {
+        struct clk_hw hw;
+        struct regmap *regmap;
+        unsigned int div_offset;
+        u64 max_freq;
+        u64 fxtal;
+        unsigned int n1;
+        unsigned int hs_div;
+        u64 rfreq;
+        u64 frequency;
+        struct i2c_client *i2c_client;
+};
+#define to_clk_si570(_hw)       container_of(_hw, struct clk_si570, hw)
+
+enum clk_si570_variant {
+        si57x,
+        si59x
+};
+
+/**
+ * si570_get_divs() - Read clock dividers from HW
+ * @data:       Pointer to struct clk_si570
+ * @rfreq:      Fractional multiplier (output)
+ * @n1:         Divider N1 (output)
+ * @hs_div:     Divider HSDIV (output)
+ * Returns 0 on success, negative errno otherwise.
+ *
+ * Retrieve clock dividers and multipliers from the HW.
+ */
+static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
+                unsigned int *n1, unsigned int *hs_div)
+{
+        int err;
+        u8 reg[6];
+        u64 tmp;
+
+        err = regmap_bulk_read(data->regmap, SI570_REG_HS_N1 + data->div_offset,
+                        reg, ARRAY_SIZE(reg));
+        if (err)
+                return err;
+
+        *hs_div = ((reg[0] & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
+        *n1 = ((reg[0] & N1_6_2_MASK) << 2) + ((reg[1] & N1_1_0_MASK) >> 6) + 1;
+        /* Handle invalid cases */
+        if (*n1 > 1)
+                *n1 &= ~1;
+
+        tmp = reg[1] & RFREQ_37_32_MASK;
+        tmp = (tmp << 8) + reg[2];
+        tmp = (tmp << 8) + reg[3];
+        tmp = (tmp << 8) + reg[4];
+        tmp = (tmp << 8) + reg[5];
+        *rfreq = tmp;
+
+        return 0;
+}
+
+/**
+ * si570_get_defaults() - Get default values
+ * @data:       Driver data structure
+ * @fout:       Factory frequency output
+ * Returns 0 on success, negative errno otherwise.
+ */
+static int si570_get_defaults(struct clk_si570 *data, u64 fout)
+{
+        int err;
+        u64 fdco;
+
+        regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);
+
+        err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
+        if (err)
+                return err;
+
+        /*
+         * Accept optional precision loss to avoid arithmetic overflows.
+         * Acceptable per Silicon Labs Application Note AN334.
+         */
+        fdco = fout * data->n1 * data->hs_div;
+        if (fdco >= (1LL << 36))
+                data->fxtal = div64_u64(fdco << 24, data->rfreq >> 4);
+        else
+                data->fxtal = div64_u64(fdco << 28, data->rfreq);
+
+        data->frequency = fout;
+
+        return 0;
+}
+
+/**
+ * si570_update_rfreq() - Update clock multiplier
+ * @data:       Driver data structure
+ * Passes on regmap_bulk_write() return value.
+ */
+static int si570_update_rfreq(struct clk_si570 *data)
+{
+        u8 reg[5];
+
+        reg[0] = ((data->n1 - 1) << 6) |
+                ((data->rfreq >> 32) & RFREQ_37_32_MASK);
+        reg[1] = (data->rfreq >> 24) & 0xff;
+        reg[2] = (data->rfreq >> 16) & 0xff;
+        reg[3] = (data->rfreq >> 8) & 0xff;
+        reg[4] = data->rfreq & 0xff;
+
+        return regmap_bulk_write(data->regmap, SI570_REG_N1_RFREQ0 +
+                        data->div_offset, reg, ARRAY_SIZE(reg));
+}
+
+/**
+ * si570_calc_divs() - Caluclate clock dividers
+ * @frequency:  Target frequency
+ * @data:       Driver data structure
+ * @out_rfreq:  RFREG fractional multiplier (output)
+ * @out_n1:     Clock divider N1 (output)
+ * @out_hs_div: Clock divider HSDIV (output)
+ * Returns 0 on success, negative errno otherwise.
+ *
+ * Calculate the clock dividers (@out_hs_div, @out_n1) and clock multiplier
+ * (@out_rfreq) for a given target @frequency.
+ */
+static int si570_calc_divs(unsigned long frequency, struct clk_si570 *data,
+                u64 *out_rfreq, unsigned int *out_n1, unsigned int *out_hs_div)
+{
+        int i;
+        unsigned int n1, hs_div;
+        u64 fdco, best_fdco = ULLONG_MAX;
+        static const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
+
+        for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
+                hs_div = si570_hs_div_values[i];
+                /* Calculate lowest possible value for n1 */
+                n1 = div_u64(div_u64(FDCO_MIN, hs_div), frequency);
+                if (!n1 || (n1 & 1))
+                        n1++;
+                while (n1 <= 128) {
+                        fdco = (u64)frequency * (u64)hs_div * (u64)n1;
+                        if (fdco > FDCO_MAX)
+                                break;
+                        if (fdco >= FDCO_MIN && fdco < best_fdco) {
+                                *out_n1 = n1;
+                                *out_hs_div = hs_div;
+                                *out_rfreq = div64_u64(fdco << 28, data->fxtal);
+                                best_fdco = fdco;
+                        }
+                        n1 += (n1 == 1 ? 1 : 2);
+                }
+        }
+
+        if (best_fdco == ULLONG_MAX)
+                return -EINVAL;
+
+        return 0;
+}
+
+static unsigned long si570_recalc_rate(struct clk_hw *hw,
+                unsigned long parent_rate)
+{
+        int err;
+        u64 rfreq, rate;
+        unsigned int n1, hs_div;
+        struct clk_si570 *data = to_clk_si570(hw);
+
+        err = si570_get_divs(data, &rfreq, &n1, &hs_div);
+        if (err) {
+                dev_err(&data->i2c_client->dev, "unable to recalc rate\n");
+                return data->frequency;
+        }
+
+        rfreq = div_u64(rfreq, hs_div * n1);
+        rate = (data->fxtal * rfreq) >> 28;
+
+        return rate;
+}
+
+static long si570_round_rate(struct clk_hw *hw, unsigned long rate,
+                unsigned long *parent_rate)
+{
+        int err;
+        u64 rfreq;
+        unsigned int n1, hs_div;
+        struct clk_si570 *data = to_clk_si570(hw);
+
+        if (!rate)
+                return 0;
+
+        if (div64_u64(abs(rate - data->frequency) * 10000LL,
+                                data->frequency) < 35) {
+                rfreq = div64_u64((data->rfreq * rate) +
+                                div64_u64(data->frequency, 2), data->frequency);
+                n1 = data->n1;
+                hs_div = data->hs_div;
+
+        } else {
+                err = si570_calc_divs(rate, data, &rfreq, &n1, &hs_div);
+                if (err) {
+                        dev_err(&data->i2c_client->dev,
+                                        "unable to round rate\n");
+                        return 0;
+                }
+        }
+
+        return rate;
+}
+
+/**
+ * si570_set_frequency() - Adjust output frequency
+ * @data:       Driver data structure
+ * @frequency:  Target frequency
+ * Returns 0 on success.
+ *
+ * Update output frequency for big frequency changes (> 3,500 ppm).
+ */
+static int si570_set_frequency(struct clk_si570 *data, unsigned long frequency)
+{
+        int err;
+
+        err = si570_calc_divs(frequency, data, &data->rfreq, &data->n1,
+                        &data->hs_div);
+        if (err)
+                return err;
+
+        /*
+         * The DCO reg should be accessed with a read-modify-write operation
+         * per AN334
+         */
+        regmap_write(data->regmap, SI570_REG_FREEZE_DCO, SI570_FREEZE_DCO);
+        regmap_write(data->regmap, SI570_REG_HS_N1 + data->div_offset,
+                        ((data->hs_div - HS_DIV_OFFSET) << HS_DIV_SHIFT) |
+                        (((data->n1 - 1) >> 2) & N1_6_2_MASK));
+        si570_update_rfreq(data);
+        regmap_write(data->regmap, SI570_REG_FREEZE_DCO, 0);
+        regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_NEWFREQ);
+
+        /* Applying a new frequency can take up to 10ms */
+        usleep_range(10000, 12000);
+
+        return 0;
+}
+
+/**
+ * si570_set_frequency_small() - Adjust output frequency
+ * @data:       Driver data structure
+ * @frequency:  Target frequency
+ * Returns 0 on success.
+ *
+ * Update output frequency for small frequency changes (< 3,500 ppm).
+ */
+static int si570_set_frequency_small(struct clk_si570 *data,
+                                     unsigned long frequency)
+{
+        /*
+         * This is a re-implementation of DIV_ROUND_CLOSEST
+         * using the div64_u64 function lieu of letting the compiler
+         * insert EABI calls
+         */
+        data->rfreq = div64_u64((data->rfreq * frequency) +
+                        div_u64(data->frequency, 2), data->frequency);
+        regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_FREEZE_M);
+        si570_update_rfreq(data);
+        regmap_write(data->regmap, SI570_REG_CONTROL, 0);
+
+        /* Applying a new frequency (small change) can take up to 100us */
+        usleep_range(100, 200);
+
+        return 0;
+}
+
+static int si570_set_rate(struct clk_hw *hw, unsigned long rate,
+                unsigned long parent_rate)
+{
+        struct clk_si570 *data = to_clk_si570(hw);
+        struct i2c_client *client = data->i2c_client;
+        int err;
+
+        if (rate < SI570_MIN_FREQ || rate > data->max_freq) {
+                dev_err(&client->dev,
+                        "requested frequency %lu Hz is out of range\n", rate);
+                return -EINVAL;
+        }
+
+        if (div64_u64(abs(rate - data->frequency) * 10000LL,
+                                data->frequency) < 35)
+                err = si570_set_frequency_small(data, rate);
+        else
+                err = si570_set_frequency(data, rate);
+
+        if (err)
+                return err;
+
+        data->frequency = rate;
+
+        return 0;
+}
+
+static const struct clk_ops si570_clk_ops = {
+        .recalc_rate = si570_recalc_rate,
+        .round_rate = si570_round_rate,
+        .set_rate = si570_set_rate,
+};
+
+static bool si570_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+        switch (reg) {
+        case SI570_REG_CONTROL:
+                return true;
+        default:
+                return false;
+        }
+}
+
+static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
+{
+        switch (reg) {
+        case SI570_REG_HS_N1 ... (SI570_REG_RFREQ4 + SI570_DIV_OFFSET_7PPM):
+        case SI570_REG_CONTROL:
+        case SI570_REG_FREEZE_DCO:
+                return true;
+        default:
+                return false;
+        }
+}
+
+static struct regmap_config si570_regmap_config = {
+        .reg_bits = 8,
+        .val_bits = 8,
+        .cache_type = REGCACHE_RBTREE,
+        .max_register = 137,
+        .writeable_reg = si570_regmap_is_writeable,
+        .volatile_reg = si570_regmap_is_volatile,
+};
+
+static int si570_probe(struct i2c_client *client,
+                const struct i2c_device_id *id)
+{
+        struct clk_si570 *data;
+        struct clk_init_data init;
+        struct clk *clk;
+        u32 initial_fout, factory_fout, stability;
+        int err;
+        enum clk_si570_variant variant = id->driver_data;
+
+        data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        init.ops = &si570_clk_ops;
+        init.flags = CLK_IS_ROOT;
+        init.num_parents = 0;
+        data->hw.init = &init;
+        data->i2c_client = client;
+
+        if (variant == si57x) {
+                err = of_property_read_u32(client->dev.of_node,
+                                "temperature-stability", &stability);
+                if (err) {
+                        dev_err(&client->dev,
+                                  "'temperature-stability' property missing\n");
+                        return err;
+                }
+                /* adjust register offsets for 7ppm devices */
+                if (stability == 7)
+                        data->div_offset = SI570_DIV_OFFSET_7PPM;
+
+                data->max_freq = SI570_MAX_FREQ;
+        } else {
+                data->max_freq = SI598_MAX_FREQ;
+        }
+
+        if (of_property_read_string(client->dev.of_node, "clock-output-names",
+                        &init.name))
+                init.name = client->dev.of_node->name;
+
+        err = of_property_read_u32(client->dev.of_node, "factory-fout",
+                        &factory_fout);
+        if (err) {
+                dev_err(&client->dev, "'factory-fout' property missing\n");
+                return err;
+        }
+
+        data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
+        if (IS_ERR(data->regmap)) {
+                dev_err(&client->dev, "failed to allocate register map\n");
+                return PTR_ERR(data->regmap);
+        }
+
+        i2c_set_clientdata(client, data);
+        err = si570_get_defaults(data, factory_fout);
+        if (err)
+                return err;
+
+        clk = devm_clk_register(&client->dev, &data->hw);
+        if (IS_ERR(clk)) {
+                dev_err(&client->dev, "clock registration failed\n");
+                return PTR_ERR(clk);
+        }
+        err = of_clk_add_provider(client->dev.of_node, of_clk_src_simple_get,
+                        clk);
+        if (err) {
+                dev_err(&client->dev, "unable to add clk provider\n");
+                return err;
+        }
+
+        /* Read the requested initial output frequency from device tree */
+        if (!of_property_read_u32(client->dev.of_node, "clock-frequency",
+                                &initial_fout)) {
+                err = clk_set_rate(clk, initial_fout);
+                if (err) {
+                        of_clk_del_provider(client->dev.of_node);
+                        return err;
+                }
+        }
+
+        /* Display a message indicating that we've successfully registered */
+        dev_info(&client->dev, "registered, current frequency %llu Hz\n",
+                        data->frequency);
+
+        return 0;
+}
+
+static int si570_remove(struct i2c_client *client)
+{
+        of_clk_del_provider(client->dev.of_node);
+        return 0;
+}
+
+static const struct i2c_device_id si570_id[] = {
+        { "si570", si57x },
+        { "si571", si57x },
+        { "si598", si59x },
+        { "si599", si59x },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, si570_id);
+
+static const struct of_device_id clk_si570_of_match[] = {
+        { .compatible = "silabs,si570" },
+        { .compatible = "silabs,si571" },
+        { .compatible = "silabs,si598" },
+        { .compatible = "silabs,si599" },
+        { },
+};
+MODULE_DEVICE_TABLE(of, clk_si570_of_match);
+
+static struct i2c_driver si570_driver = {
+        .driver = {
+                .name = "si570",
+                .of_match_table = of_match_ptr(clk_si570_of_match),
+        },
+        .probe          = si570_probe,
+        .remove         = si570_remove,
+        .id_table       = si570_id,
+};
+module_i2c_driver(si570_driver);
+
+MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
+MODULE_AUTHOR("Soeren Brinkmann <soren.brinkmann@xilinx.com");
+MODULE_DESCRIPTION("Si570 driver");
+MODULE_LICENSE("GPL");